In the area of separation materials, there are a family of resins that contain metal ligands. The majority of these are aimed at the separation of proteins. Examples of conventional commercial resins are Sephadex (GE Healthcare), BioGel (BioRad) and Toyopearl (Tosoh). These conventional resins generally have a low cross-linking degree and a flexible backbone structure, and comprise large pores. The large pores are optimized for analytes such as proteins but none of the mentioned conventional materials offers a satisfactory solution for certain types of small molecules. Conventional chelate materials that have been developed for small molecules, such as Purolite® chelation resins, are conventionally used for the separation of small molecules that interact with metal ions. Said materials sometimes lead to poor separations, low selectivity and unsatisfactory resolutions for certain applications areas. Othermetal chelate resins, such as Dowex 50WX8, Amberlite® CG50, Amberlite® IR-120, Amberlyst® 15, although widely used do not always perform satisfactorily when used for demanding separations, such as pesticides and other environmental contaminants present at low concentrations in complex matrices.
The use of silver-loaded cation exchangers for purifying and separating unsaturated small molecules, e.g. fatty acids, pheromones and polyaromatic sulphur-containing heterocycles, has been described and such resins have been used in column chromatography systems for analytical and preparative purposes. Within the food industry it is generally a requirement that food raw materials, components or products are not contaminated by metals during processing.
Several studies described in the literature have shown that the hydrolysis reactions of pesticides may be catalysed by metals in an aqueous environment. However, hydrolysis does not completely solve the problem of removing the pesticides as it does not remove the hydrolysis products that are formed.
Ridvan Say in Anal. Chim. Acta 579 (2006) 74-80 discloses molecularly imprinted polymers prepared using paraoxan or parathion as template and methacryloyl-antipyrine-gadolinium chelate as a monomer.
Removal of pesticides from food is a major focus within the food industry and there is increasing public concern over the level of pesticide residues in food. U.S. Pat. No. 5,558,893 discloses a distillation method for contaminated citrus oils that can be used for the preparation of citrus oils that are essentially pesticide free. However, distillation generally has an adverse effect on the flavor of the citrus oils since numerous volatile compounds that impart flavor and taste are simultaneously removed.
Removal and adsorption of fungicides and herbicides in aqueous solution on modified activated carbon is used for purifying pharmaceutical oil, refineries as well as pesticides as disclosed in Separation and Purification Technology, Vol 52, Issue 3, January 2007, Pages 403-415.
Pesticides are not only a problem in citrus oils but are present in many other essential oils (e.g. palm oil). Consequently there is a need for materials and methods for selectively removing, extracting, separating and/or analysing pesticides from food and feed products, such as essential oils.